Previously, NASCAR had refused to disclose what substance Mayfield tested positive for, and blacked out the name of the drug in all court filings leading up to Wednesday's hearing, which was attended by NASCAR chairman Brian France and president Mike Helton.

France said the organization has no immediate plans to file an appeal, but he didn't rule it out.

"We are disappointed, but we respect the judge's ruling," NASCAR spokesman Ramsey Poston said in a statement. "This is only a temporary injunction. The legal case continues beyond this point, and we will continue to make our case."

Associated PressNASCAR driver Jeremy Mayfield, right, smiles as he leaves the federal courthouse with his attorney, Bill Diehl, in Charlotte, N.C., on Wednesday. A judge lifted Mayfield's suspension, saying he should be allowed to race at Daytona this weekend.

Mayfield's attorneys argued Wednesday that Mayfield has never shown any characteristics of a meth abuser and that he never had the opportunity to get his backup "B" sample tested by an independent laboratory.

Mullen said NASCAR can test Mayfield extensively, including hair samples, to determine "if he's been a meth head or not."

Outside the courtroom, Poston said NASCAR would indeed test Mayfield if he's in Daytona Beach, Fla., this weekend.

Whether Mayfield will field a car is still a question. After the ruling he said he would definitely be at the speedway but has to work out the money for his race team to be there, too.